Domain controller (dc1) running Windows 2003 with DNS server and DHCP server.
In the DHCP scope DNS option tab, there are two choices:
[v] Enable DNS dynamic updates according to the settings below:
(v) Dynamically update DNS A and PTR records only requested by the DHCP clients
() Always dynamically update DNS A and PTR records
[v] Discard A and PTR records when lease is deleted
 Dynamically update DNS A and PTR records fro DHCP clients that do not request updates (for example, clients running Windows NT 4)
(v means my current settings.)
I see that NT4 clients get IP from DHCP server, but DNS record is not updated.
I also see old DNS record in the list. For example, non-live host with some IP. Lease expired already.
Q#1. Should I choose 'Always dynamically update DNS A and PTR record' option?
Q#2. What options (above) should I use if I want to update DNS record dynamically?
Q#3. Under what situation is the first option (update only if requested by client)?